From Spain and Slovenia to Mexico: The Mercury Route

Posted On November 5, 2017

Whatever history I had in middle school (a very long time ago), tales of the Camino Real excited my imagination, and, when I discovered that the Camino Real had passed close to the door of my second house in San Miguel de Allende, my interest in Mexican history was forever piqued.

Bridge San Rafael L. Whynman

Each painting foray introduces me to another chapter of Mexican history. This week we painted the Bridge of San Rafael …a hop, skip and, well hidden, jump from San Miguel de Allende….one of three bridges in the state of Guanajuato that is part of the Camino Real de Tierra Adentro World Heritage Site. Luckily, we had friend and watercolorist, Rick Wendling, with us to help locate this hidden treasure.

Bridge of San Rafael L. Topinka

The Bridge of San Rafael is not considered exceptional in terms of construction but is located at an important branching of the Camino Real de Tierra Adentro that connected Queretaro and Mexico City to Guanajuato and eventually points north. The bridge was built in the 18th century. Sadly, part of it was demolished by a flood in the 19th century and only one arch of three remains. Linda painted from one side and I from the other with both of us intrigued by the reflections. If you look closely you can see the white egrets and their reflections in the water through the arch. Trees, big ones, are actually growing on top of the bridge. In both of our paintings, they are not from the background.

But another history lesson awaits…A little fuzzy about the history of the Camino Real? Check out a previous post on the Bridge of El Frailefor background as I want to continue with a fascinating story about what passed over this bridge and other parts of the Camino Real.

When the Spaniards first arrived in the Americas, they looted the gold and silver objects that had been accumulated by the indigenous people over generations. This played out quickly and the Spaniards looked for gold and silver deposits to continue the stream of precious metals from the Americas to Spain. Rich silver lodes were discovered in the mid-1500’s in central Mexico and, during the colonial period, nine times more silver was mined and refined than was gold.

Colonial Mexico used both smelting and amalgamation (discovered in 1554) to refine the silver. Smelting used trees for fuel thus denuding great parts of central Mexico and amalgamation or the “patio process” used mercury imported from the Almaden mine in Southern Spain and, to a lesser extent, from the Idrija mine in modern Slovenia.

A little aside about the amalgamation or “patio process”…..the silver ore was crushed with hydraulic stamps, sieved to form a flour, spread over large paved, flat surfaces and then mixed with water, mercury (Quicksilver), salt and other reagents. Workmen blended the mixture with hoes and rakes and left it until the silver amalgamated with the mercury. The rubbish was then washed away, and the mercury squeezed out or distilled for re-use. A lump of relatively pure silver remained ready to be fired and cast into bars. Not all mercury was recovered and thus the continuous need for more mercury as well as the ongoing contamination of surrounding land and water

Mercury is deadly to all living things.

From 1570 to 1820, 67,970 tonnes of liquid mercury were shipped from Spain and Slovenia to Mexico or about 1,359,400 US gallons. (I think I did the math correctly. Anyway a lot of mercury!)

Remember playing with those balls of liquid mercury usually from broken thermometers….according to the EPA only 1/70th of a teaspoon of mercury is needed to contaminate a 25-acre lake to the point where the fish are unsafe to eat. Today, millions of kilograms of mercury lie beneath the soil in dozens of colonial mining sites in Mexico potentially polluting groundwater and farmers’ fields. Particularly concerning are the low-lying agricultural areas in the Zacatecas Plateau where rivers have dispersed the residues from colonial mining activities.

Mercury is with us in one of its forms forever. It cannot be destroyed.

An artistic aside….in China mercury ore (cinnabar)was used to make the color vermilion.

Three bridges in the state of Guanajuato are officially listed in UNESCO documents as part of The Camino Real de Tierra Adentro World Heritage Site: El Fraile, N20 50 33.00 W100 47 55.00; San Rafael, N20 56 28.00 W100 47 37.00; and La Quemada, N21 19 40.00 W101 5 47.00.

5 Comments

Wonderful renderings of the hidden bridge; I can sense the fluidity of the water. And the egrets! plus reflections.
Thanks for sharing both your paintings and the history of silver- teasing, so sad the contamination.

So glad that you explained that those trees were actually growing ON the bridge – amazing! And yes! I definitely remember playing with those little balls of mercury — yikes! If only you had been my history teacher, I might have enjoyed it more! THANK YOU once again!